Characteristics of Thiol:Protein Disulfide Oxidoreductase from Wheat (Triticum aestivum L.) Grain

Abstract

Biochemical properties of a homogenous preparation of thiol:protein disulfide oxidoreductase (TPDO, EC 1.8.4.2) isolated for the first time from mature wheat (Triticum aestivum L.) grain were studied. According to polyacrylamide gel electrophoresis data, the molecular weight of TPDO is around 167 kD, the enzyme consisting of two subunits of 77 and 73 kD, which differentiates TPDO from known enzymes of SH/SS-metabolism of wheat caryopses. In substrate specificity and enzymatic characteristics (pH and temperature optima) TPDO is similar to analogous enzymes of animal tissues. Inhibition of disulfide reductase activity by alkylating agents and heavy metal ions suggests the participation of active center SH-groups in the catalytic act and classes the enzyme as a member of the thioredoxin superfamily. The SS-reductase reduces aggregating capacity of acetic acid-soluble fraction of wheat storage proteins. The proposed physiological role of TPDO is participation in creation and regulation of SH/SS-status of wheat endosperm proteins and formation of the rheological properties of gluten.

Relationship between Endogenous Protein Disulfide Isomerase Family Proteins and Glutenin Macropolymer

“…d 0 Aloisio et al reported the cloning, chromosomal assignment, sequencing, and expression analysis of the complete set of genes encoding the PDI and PDI-like proteins in bread wheat (36). Among these genes, only group II (i.e., TaPDIL2-1) has been identified and purified (37). After quantifying nine wheat PDI and PDI-like gene transcripts, the presence of TaPDIL1-1, TaPDIL2-1, TaP-DIL4-1, TaPDIL5-1, TaPDIL6-1, TaPDIL7-1, and TaPDIL8-1 transcripts was detected in 38 day postanthesis caryopses, when the deposition of seed storage reserves decreased and seeds began the process of desiccation (36).…”

Role of Non-prolamin Proteins and Low Molecular Weight Redox Agents in Protein Folding and Polymerization in Wheat Grains and Influence on Baking Quality Parameters

“…72 The optimum temperature for TPDO activity was established at 36 °C. 70 Gluten weakening was observed in wheat growing at high temperatures (37/28 °C, day/night) 73,74 and might be connected to the activity of enzymatic systems that are similar to those of TPDO.…”

“…We managed to extract and purify a GSH-dependent protein, thiol:protein-disulfide oxidoreductase (TPDO, EC 1.8.4.2), from wheat grain; this protein catalyzed the cleavage of disulfide bonds in acetic-soluble gluten proteins (Figure ) and reduced their capacity to aggregate . The enzyme was classified as a Grx-like protein because the molecular masses of the native TPDO protein (approximately 167 kDa) and its two subunits (77 and 73 kDa) significantly exceeded the molecular mass of typical glutaredoxins (12–14 kDa) and typical wheat PDI (60 kDa) . The maximum level of TPDO activity occurred between the third and fifth weeks after anthesis (WAA), in a period of maximum synthesis of storage proteins in wheat kernels.…”

“…Mapping of the activity level of endogenous TPDO was performed using an International Triticeae Mapping Initiative mapping population and revealed chromosomal loci (QTLs) associated with TPDO activity and dough physical properties, such as flour strength, elasticity, and water-absorbing capacity . The optimum temperature for TPDO activity was established at 36 °C . Gluten weakening was observed in wheat growing at high temperatures (37/28 °C, day/night) , and might be connected to the activity of enzymatic systems that are similar to those of TPDO.…”